Rotary drum sanders are typically used in wood-working projects, wherein the drum is rotatably mounted on a vertically-adjustable assembly, positioned over a horizontal bed. A workpiece is moved across the horizontal bed through the adjustable gap between the drum and the bed, so that the surface of the workpiece may be contacted by the drum as it passes through the gap. The gap is typically adjusted to be slightly narrower than the thickness of the workpiece, to permit the sanding material on the surface of the drum to abrade the workpiece.
The workpiece may be moved over the horizontal bed using an abrasive belt that travels over the bed. The outward-facing abrasive surface of the belt helps move the workpiece due to friction forces between the belt and the workpiece. The belt may for example be arranged as a loop around the horizontal bed, with rollers at the ends of the bed allowing the belt to rotate. Typically, one roller will be a driving roller, connected to a motor, and the other roller will be an idle roller.
During operation of the sander, the abrasive belt often has a tendency to skew relative to the rollers. As a result, the edges of the abrasive belt will come in contact with some non-moving part of the machine, resulting in the belt being destroyed, and/or damage to the machine. Adjustment of the abrasive belt to prevent skewing is commonly a time-consuming trial-and-error process.